1. Field of the Invention
The present invention relates to a spindle motor for a disk drive apparatus.
2. Description of the Related Art
In the related art, spindle motors for disk drive apparatuses that include bearing mechanisms which use fluid dynamic pressure are used. In such a bearing mechanism, a shaft is supported by a sleeve via a lubricant. The bearing mechanism achieves low noise in this manner. In the bearing mechanism disclosed in JP-A-2005-155912, a side surface of an inner circumferential surface of a hole portion of a cover member is chamfered and is allowed to face an outer circumferential surface of a shaft such that a first tapered seal portion, which is a tapered seal on an inner side, is formed and a second tapered seal portion, which is a tapered seal portion on an outer side, is formed between an outer circumferential side surface of the cover member and an inner circumferential surface of a housing. The bearing mechanism described above discloses a technique for holding the lubricant, which is used in a fluid dynamic pressure bearing mechanism, with the first tapered seal portion and the second tapered seal portion while sequentially circulating the lubricant along an inner side surface, a lower surface, an outer side surface, and an upper surface of a sleeve.
In the bearing mechanism described above, the surface area of a liquid surface of the lubricant that is in contact with outside air increases since the lubricant is held by the two tapered seal portions, which causes the lubricant to evaporate in quantity. When the lubricant evaporates, the lubricant becomes absent between the shaft and the sleeve to cause the shaft and the sleeve to come into contact with each other and cause problems such as wear. Accordingly, a structure suppressing the evaporation of the lubricant is required.